A field of particular interest for the application of the invention is that of sport boots such as snow-boarding, trekking, and skating boots and the like. These types of sport boots have uppers that are quite stiff and elongated and the fastenings of which have to satisfy the conflicting requirements of quick and effective tightening and equally quick and'effective loosening. However, the technical teachings provided by the invention are applicable to footwear of different types with preferred use in boots which require a fairly long fastening and a fairly stiff upper.
Amongst the known advantages of lace fastenings is that of creating a homogeneous closure for the foot along the entire extent of the edges of the access opening of the footwear. However, to achieve this, each of the edges of the footwear must carry a respective plurality of lacing eyes arranged fairly close together. Arranging the lacing eyes close together, however, leads to an increase in the angle formed by the lace as it extends into and out of the eyes, which in turn causes greater friction between the lace and the lacing eyes. For this reason, it is not generally possible to fasten (or, on the other hand, to loosen) the fastening simply by exerting a pull on the ends of the lace, but it is necessary to pull on intermediate portions of the lace in order to distribute the pulling load along the entire fastening. Lacing-eye devices and members of particular shapes and designs have been investigated to minimize the effects of the friction between the lacing eyes and the lace. For example, lacing eyes provided with pulleys, with resin inserts having a low coefficient of friction, or with curved profiles have been produced but, in parallel with possible advantages in terms of the ability of the lace to slide, all these involve other disadvantages. In particular, these special devices are bulky and/or delicate and therefore respond poorly either to the need for strength for heavy uses and/or for use in difficult environmental conditions, or to the more typically decorative requirements of the footwear. Moreover, their efficacy in reducing the above-mentioned friction is only partial, to the extent that it is not normally possible, even with relatively short fastenings, to tighten the footwear simply by pulling on the ends of the laces.
US Patent Publication No. 2003/0034365A1 and U.S. Pat. No. 6,467,195 describe sports footwear with lace fastenings in which the two ends of the lace converge in a grip for preventing soreness of the user's hand during the tightening of the fastening.
US Patent Publication No. 2003/0051374 A1 describes a double-lace fastening in which all of the ends of the laces extend through a single edge of the fastening and converge in a strap which in turn can be fixed releasably to the footwear upper beyond the opposite edge. This fastening is suitable exclusively for shoes with a limited number of lacing eyes since it does not permit a high lacing tension to be exerted on the ends of the laces. It also causes non-homogeneous lacing tensions on the two laces since they follow different paths and are of different lengths. In practice, various shapes of users' feet cause a different length of lace to be engaged in the lacing eyes according to the position occupied along the opening to be closed so that, once the fastening is closed, the free ends of the laces are not necessarily of equal length.